docs: def _add_common_constrain(token_lst: List[Dict], d: Dict) -> List[Dict]:
          """
          Add common constrain for every token type, like "is_required"
          Args:
              token_lst: List[Dict]
              d: Dict
  
          Returns: List[Dict]
          """
  
          result = []
          for a_token in token_lst:
              if not tf_transfer(d["is_required"]):
                  a_token["OP"] = "?"
              result.append(a_token)
          return result